This invention relates to a gasket particularly but not exclusively intended for sealing the joint between the cylinder block and the cylinder head of a wet liner internal combustion engine.
In my co-pending patent application Ser. No. 930,429, now U.S. Pat. No. 4,203,608, there is described an improved form of gasket which is suitable for use in dry liner internal combustion engines.
However, unfortunately, this particular form of gasket has been found to be unsuitable for use in wet liner internal combustion engines. The reason for this is that in the production of wet liner internal combustion engines the cylinder bore liners have essentially to protrude beyond the face of the cylinder block rather than to terminate below it. The criteria to be satisfied by the gasket are twofold, namely (a) that there should be a sufficient load on the liner to make a gas seal and (b) that there should not be an excessive load such as would cause the rim of the liner to fracture from the liner wall. The consequence of any attempt to seal the liner also using a gasket as previously proposed is that the load on the liner rim would be greatly excessive.
A theoretical solution to the problem would be to use a gasket of the kind disclosed in my above-mentioned co-pending application and to machine the central noncorrugated metal sheet thereof around each of the cylinder bores to allow for liner protrusion. This is however not practical because of the machining tolerances which are necessary.
The present invention is based upon the realization that there should be an independent seal or sealing element for each of the cylinder bores of a wet liner engine. Any such sealing element must possess the ability to apply a high, but not excessive, unit load, that is to say the clamping load needs to be concentrated in a closely defined area. Also, because of varying heights of liner rim from one engine or cylinder bore to another such a sealing element must be able to cope with quite substantial variations.
A gasket incorporating firstly a solid soft washer, and secondly, a soft washer formed around its perimeter with a multiplicity of closely spaced perforations parallel to its axis proved unsatisfactory. In the first instance the load on the rim has to be far too great in order to form a successful gas seal, and in the second instance the washer spreads both radially inwards and radially outwards which is unacceptable.